Adaptation, Exaptation, By-Products and Spandrels in Evolutionary Explanations of Morality more

PENULTIMATE DRAFT, FINAL VERSION PUBLISHED IN BIOLOGICAL THEORY 5(3) Adaptation, exaptation, by-products & spandrels in evolutionary explanations of morality Ben Fraser 9/25/2011 Adaptationist accounts of morality attempt to explain the evolution of morality in terms of the selective advantage that judging in moral terms secured for our ancestors (e.g. Ruse 1998; Joyce 2006; Street 2006). So-called by-product explanations of morality have been presented as an alternative to adaptationist accounts (e.g. Prinz 2009; Ayala 2010; cf. Darwin 2004/1871). In assessing the relationship between adaptationist and by-product accounts, care must be taken to distinguish several related but importantly different notions: innateness, adaptation, exaptation, spandrel, and by-product. Adaptationist Accounts of Morality A great deal of interesting work has been done under the heading of evolutionary explanation of morality. Many hurdles – both empirical and conceptual – confront work of this kind, one being the question of how to specify the target of such an explanation. Some researchers focus on certain kinds of behaviour (Wilson 2000/1975), while others consider group-level phenomena like systems of norms (Boyd & Richerson 2005), and yet others devote their attention to features of human psychology, such as so-called “moral sentiments” like shame and guilt (Frank 1988) or an innate “moral grammar” (Hauser 2006). The kind of evolutionary explanation of morality I will focus on here targets the trait of making moral judgments. Those who offer such an explanation include Michael Ruse (1998), Sharon Street (2006), and Richard Joyce (2006). One key claim made in evolutionary explanations of morality that target the trait of judging in moral terms is that moral thinking is motivationally powerful thinking; making a moral judgment to the effect that some act is obligatory increases the chances of one performing that act, while judging an act to be morally impermissible makes it more likely that one will refrain from that act. Another key claim is that the kinds of acts we tend to evaluate in a morally positive light are predominantly helpful, cooperative acts that would have been fitness-enhancing for our distant ancestors, who lived among close kin and whose small-scale social worlds importantly included networks of reciprocal relationships. These two claims together form the core of an evolutionary explanation for morality. For instance, Ruse claims that “because it is biologically advantageous for us to help and co-operate, morality… has evolved to guide and stiffen our will” (1998: 222). Along similar lines, Joyce claims that “the actions that morality prescribes with categorical force are those that constitute or promote, roughly speaking, cooperation” (2000: 714). Finally, Street claims that “certain kinds of evaluative judgements… contributed to our ancestors’ reproductive success… because they forged adaptive links between our ancestors’ circumstances and their responses to those circumstances, getting them to act, feel, and believe in ways that turned out to be reproductively advantageous” (2006: 127). In essence, what I will call adaptationist evolutionary explanations of morality hold that human morality – meaning the trait of making moral judgments – is an adaptation. Those who offer adaptationist explanations of morality may differ over empirical details, such as what the function of morality is supposed to be, and over the philosophical implications of the explanation, in particular its implications for metaethics. They are united, however, in thinking that we can understand why it is we are creatures who judge in moral terms by considering the fitness benefits of so judging enjoyed by our distant ancestors. The By-Product Explanation for Morality Adaptationist explanations of morality hold that the trait of making moral judgements evolved because such judgements effectively motivated fitness-enhancing helpful behaviour. An alternative to adaptationist explanation in evolutionary biology is explanation of some trait as a by-product of other traits that are adaptations. Byproduct explanations are far from unknown, even when the trait in question is of the utmost interest and importance in human mental and social life. Stephen Gould, for instance, suggested that: [M]any universal features of human cognition—the primary data of evolutionary psychology—probably arise as spandrels of a general consciousness evolved for other reasons (almost surely adaptive). Freud argued that our fear of death acts as a key inspiration for the universal human institution of religion (for which many adaptationist explanations have been proposed, largely in the speculative mode). But I don't see how a biologist could argue that the human brain evolved consciousness in order to teach us that we must die. Knowledge of death is therefore probably a spandrel—an ineluctable consequence of consciousness evolved for other reasons. But this spandrel may then have inspired one of our defining institutions (Pinker et al. 1997). By-product explanations for morality are not unknown either, and even if they are uncommon (as noted by Fitzpatrick 2008) they are not for that reason uninteresting. Darwin’s discussion of the human moral sense in The Descent of Man at times sounds notes in harmony with the by-product account. More recently, biologist Francisco Ayala (2010) has offered a by-product explanation for morality. Another who has championed a by-product explanation of morality as a rival to adaptationist accounts is philosopher Jesse Prinz (2007a; 2007b; 2008a; 2008b; 2009). I will focus on Prinz’s discussion, since he gives the by-product account a sustained articulation and also because he can serve as a character in something of a cautionary tale about the care that must be taken in developing by-product explanations. According to Prinz, the fact that we make moral judgements is “an evolutionary accident”, a “by-product of capacities that were evolved for other purposes” (Prinz 2009: 168). Prinz considers his by-product explanation a rival to the adaptationist account offered by Ruse, Joyce, Street and the like, on which “morality is an evolved capacity” (Prinz 2009: 168). He writes: [Our] capacity to moralise could be an evolved adaptation that occurred after we split from the ancestor that we share with chimpanzees. Or, alternatively, the capacity to moralise could be a by-product of other capacities, which evolved for other purposes (2007a: 263, emphasis added). Prinz thinks the latter option is the correct one, and that the adaptationist approach to the evolution of morality taken by Ruse, Joyce, Street and the like is therefore mistaken. To begin our discussion of Prinz’s by-product explanation, it is worth quoting him at some length, since responding to his claims is largely a matter of clarifying material too densely and swiftly presented. He writes: It seems…that we have good evidence for the claim that morality is an evolved capacity. Animals may not have moral systems in exactly the same sense that we do, but the resemblance is intriguing. It is tempting to conclude that human morality is an evolutionary successor to capacities found in other species. On the [sic] picture, morality is innate. We are born to be good. The concept of innateness is closely related to domain specificity. To say that a capacity is innate is, in part, to say that we have biological machinery dedicated to attainment of that capacity. Friends of innateness claims often emphasise universals. If morality is part of the bioprogram, and the evolved aspects of human psychology are generally monomorphic, then there must be moral universals, i.e. there must be aspects of our moral systems that are found amongst all normally developing members of our species (2009: 168). Prinz goes on to say that the claim that there are moral universals can be interpreted in three different ways (2009: 168). Firstly, “immodest moral nativism” says that the human moral universals are moral rules with specific, fixed contents. Rules against harming others and rules against incest are two of the candidate moral universals Prinz considers. “Modest moral nativism” says that all normal humans have a “morality acquisition device,” which consists of schematic moral rules and which takes inputs from culture to fill out those rules. The idea is that everyone has inscribed somehow in their mind rules like do not harm <insert subjects here>, where precisely what subjects are inserted depends on the culture in which the individual bearing the morality acquisition device develops. Finally, “minimal moral nativism” says that all normal humans have a “moralisation mechanism,” meaning a faculty which “converts” nonmoral rules to moral rules. For instances, Prinz suggests the moralization mechanism might convert a tendency to avoid incest – a brute psychological aversion – into a taboo against incest. Prinz rejects all three versions of the claim that there are human moral universals. He takes this to support the conclusion that “morality… is a byproduct of capacities that were evolved for other purposes. Morality is a spandrel. There is no mechanism dedicated to the acquisition of moral norms” (2009: 168). Prinz’s treatments of this topic in other publications reach similar conclusions, for example, that “morality… is a by-product of capacities that were not themselves evolved for the acquisition of moral rules” (2007: 270). Talk of innateness, nativism, universality, domain specificity, dedicated machinery, by-products, and spandrels comes thick and fast in Prinz’s argument for the by-product explanation, so much so that it becomes difficult to see how what he says counts against the claim that the trait of making moral judgements is an adaptation. In the end, I think, it does not. My diagnosis of the disagreement between Prinz and the likes of Joyce, Street, and Ruse is disappointingly prosaic: Prinz has fallen foul of the confusion surrounding the concept of innateness. Untangling Terminology It is not news that the term “innate” has many meanings (Griffiths 2002; 2009). Ethologist Patrick Bateson exhorted researchers tempted to use the term to “say what you mean (even if it uses a bit more space) rather than unintentionally confuse your reader by employing a word such as innate that carries so many different connotations” (1991: 22). The perils of innateness talk are certainly not news to Prinz. He acknowledges the slipperiness of the term and says what he means by it: …a psychological phenotype P is innate if it is acquired by means of psychological mechanisms that are dedicated to P, as opposed to psychological mechanisms that evolved for some other purpose or for no purpose at all (2008b: 370). Prinz is here addressing Joyce, whom he recognises uses “innate” differently, to mean “can be given an adaptive explanation in genetic terms” (Joyce 2006: 2). The somewhat baffling thing is that, having been careful to specify what is meant by “innate” in the mouths of various interlocutors, Prinz goes on to make the very mistake against which such caution is meant to ward. Prinz takes the falsity of immodest, modest, and minimal moral nativism to imply that the capacity to make moral judgements is not innate in his sense (i.e. is not subserved by dedicated machinery). The problematic move in his argument for the byproduct explanation is to then say, on that basis, that the capacity to make moral judgements is not innate in the sense of not being an adaptation. So far as I can tell, Prinz’s mistake lies in supposing that being a by-product, being a spandrel, and not being subserved by dedicated machinery are equivalent (this supposition comes through fairly clearly in the quote above from Prinz 2009: 168). Careful consideration will show that this supposition is mistaken. To set up the following discussion, a distinction must be drawn between the capacity to make moral judgements and the tendency to make moral judgements. Prinz runs the two together. Pulling them apart may seem like hair-splitting. Doing so is crucial, though, if we are to see how Prinz’s case for the by-product explanation fails. I will take “the capacity to make moral judgements” to refer to the ability to make moral judgements and to whatever psychological machinery underlies that ability. I will take “the tendency to make moral judgements” to refer to the practice of actually using the capacity to make moral judgements, and will consider this to be synonymous with “the trait of making moral judgements” and with “moralising.” Having distinguished that capacity for moral judgement from moralising, the next step is to get clear on the notion of a spandrel. The term was introduced into biology by Gould & Lewontin (1979) who drew it from architecture, where it referred to the triangular spaces between the supporting arches of a dome. These spaces are present in buildings not by architectural design but because designed features of buildings necessitate their presence: spandrels “are necessary architectural by-products of mounting a dome on rounded arches” (1979: 581). Gould & Lewontin used “spandrel” to refer to features of an organism that are present, not as the result of natural design (i.e. selection for those features) but as a necessary consequence of other features being present. The human chin, for example, must exist, given that the human jawbone develops in the way it does. Chins are spandrels. Prinz follows Gould & Lewontin in his definition of spandrels: “capacities that emerge as inevitable by-products of other capacities” (2009: 183). Recall, Prinz’s view is that “morality is a spandrel” (2009: 168). If there is no mental machinery dedicated to morality, then it may well follow that the capacity to make moral judgements is a spandrel. From this, however, it does not follow that moralising is a spandrel. Consider the claim that the making of moral judgements is inevitable – it must occur – given that we have certain other capacities. Darwin himself at times suggested something like this spandrel view of morality. He wrote: Any animal whatever, endowed with well-marked social instincts, the parental and filial affections being here included, would inevitably acquire a moral sense or conscience, as soon as its intellectual powers had become as well developed, or nearly as well developed, as in man (2004/1871: 71-72). Like Darwin, Francisco Ayala think moralizing follows inevitably once a certain level of intellectual ability is achieved. Ayala claims that the human “moral sense”, which “consists of judging certain actions as either right or wrong”: …emerges as a necessary implication of our high intellectual powers, which allow us to anticipate the consequences of our actions, to evaluate such consequences, and to choose accordingly how to act (2010: 9019). Is it, however, true that social creatures, upon attaining some requisite level of intelligence, will inevitably begin to moralise, to judge certain actions to be forbidden, others obligatory, certain character traits virtuous, others vicious, and so on? There seems to be little in the way of evidence for this necessity claim. We have no comparably intelligent, social creatures here on Earth to examine. No alien species suitable for testing the claim have yet deigned to visit us. If we resort to intuitionmongering, it does not strike me, at least, as impossible that a species might reach exalted heights of intelligence without ever conceiving the notions of duty, desert, or obligation. Unlike Darwin and Ayala, Prinz thinks it is not intelligence (however that is to be defined) but, crucially, emotion, out of which moralising springs. He thinks human morality is a by-product of our emotional capacities together with our capacities for rule-formation, memory, imitation, and mind-reading (2007: 270-272). At this point, it must be noted that Prinz has a particular conception of what moralizing involves: …a person regards something as morally wrong (impermissible) if, on careful consideration, she would feel emotions of disapproval [i.e. guilt, shame, disappointment, anger, resentment, indignation, contempt or disgust] toward those who did the thing in question (2009: 179). On this “sentimentalist” account of what moralising is, it may well be inevitable that creatures will the capacities Prinz mentions are bound to moralise. I will not debate sentimentalism here. I am content to have shown that accepting Prinz’s claim that morality is a spandrel seems to depend on accepting his claim that moralizing is simply a matter of being disposed to experience certain emotions. To the extent that one thinks there is more to making moral judgments than that, one should be reluctant to agree with Prinz that morality is a spandrel. Let us pause and take stock. Suppose Prinz is right that there is no dedicated moral mental machinery, that moral judgements are made using capacities evolved for other purposes. Even so, I have claimed, the right conclusion to draw need not be that the trait of making moral judgements is a spandrel. I want to now suggest that the concept to reach for instead may be exaptation. Gould & Lewontin employed the concept of exaptation in their 1979 paper, calling it “secondary adaptation” or the “fruitful use of available parts” (1979: 596, 584). Gould later coined the term “exaptation” in a paper written with Elisabeth Vrba, defining exaptations as “useful… characters, evolved for other usages (or for no function at all), and later ‘coopted’ for their current role” (1982: 6). Gould & Vrba seem to think of exaptations as coming about primarily as the result of selection favouring the new use of the old part. One might also suppose, though, that “exaptation” could be sensibly applied in cases where intelligent agents consciously choose to employ structures that have one (or no) function for a new and useful purpose. For example, Mack truck drivers talk of “following the dog”: using their vehicle’s characteristic hood ornament as a guide when manoeuvring. Apparently, the alignment of the dog with respect to a given reference point gives the driver an accurate overall sense of how his truck is positioned with respect to that point. The function of the dog ornament is, so far as Mack truck designers are concerned, purely decorative. The fruitful use of an available part involved in following the dog might sensibly be seen as a case of cooptation of the ornament by Mack truck drivers. The ornament itself might thus sensibly be dubbed an exaptation (for manoeuvring). In any case, I will focus here on exaptations produced by natural selection rather than conscious intention. Via selection for the new use of an old part, adaptations for one purpose – or even spandrels – can be converted into adaptations for a new purpose. For example, Gould & Vrba (1982: 7-8) mention black herons (Egretta ardesiaca), which use their wings not only for flight but also to shade the water in which they wade while hunting fish. This canopy feeding method reduces glare off the water and makes prey easier to spot. The heron’s wings are adaptations for flight, which were at one stage coopted for use as water-shaders and so became exaptations for hunting and, insofar as selection has since favoured that usage, the heron’s wings have become adaptations for hunting as well. It is perhaps now clear how the notion of exaptation might figure in a response to Prinz’s case for the by-product explanation. Allow Prinz the claim that there is no mental machinery dedicated to making moral judgements. Moral judgements would then sensibly be called by-products of whichever capacities are supposed to allow, in conjunction, their production. But this would not mean that our tendency to make moral judgements – to moralise – is an evolutionary accident (as Prinz maintains) rather than an adaptation (as is claimed by the likes of Joyce and Ruse). Prinz’s supposition that a lack of dedicated machinery means an absence of adaptation is mistaken. Once we avail ourselves of the ideas of exaptation and cooptation, we can make good sense of there being adaptations that are not subserved by dedicated machinery. If we use certain faculties in combination to produce moral judgements and if (as Joyce and Ruse claim) judging in that way has been favoured by selection because of the efficacy of moralising in motivating fitness-enhancing behaviour, then the trait of making moral judgements may be an adaptation even if there is no faculty dedicated to producing moral judgements. To pause and sum up, Prinz’s claim that there is no psychological machinery dedicated to morality is compatible with adaptationist accounts of the evolution of morality. Prinz thus presents a false dichotomy when he says morality could either be “an evolved adaptation” or “a by-product” of capacities that evolved for other purposes (2007: 263). To end, I want to suggest that Prinz himself can sensibly be interpreted as offering a kind of adaptationist account of the evolution of morality, in the sense of moralising (as distinct from the capacity for doing so). Prinz writes: Very small-scale human societies may not require moral rules, because members of those societies are close enough to be naturally inclined to treat each other well. As population size grows, however, we find ourselves in contact with people who are not close friends or family. In large societies, there are often group projects, such as collective building and farming, that depend on cooperation. Mechanisms must be put in place to make sure that no one slacks off. If helping behaviour evolved in contexts where cooperative relationships were dyadic, the evolved mechanisms may not be sufficiently powerful to ensure cooperation with groups of strangers. … Moralization may have emerged as a technique to ensure that people didn’t slack off as societies grew (2007: 273). Prinz himself seems to suggest here that moralizing does have a function, namely, that of promoting in-group cooperation. It serves this function in virtue of the fact that (as the adaptationists mentioned at the start of this paper claim) moral thinking is motivationally powerful thinking that can bolster other inclinations to engage in cooperation. Were we to suppose that there has been cultural group selection acting on human societies, and that such selection favoured groups that moralized cooperation over those that did not (or did so to a lesser extent), then, we might suppose, the tendency to moralise is susceptible to adaptationist explanation. The fitness benefit here is to be found at the group level, but it would be strange to deny that the products of cultural evolution are adaptations. I am wary of reading too much into the quote given above, but I suspect that, in the final analysis, Prinz himself may be sensibly counted as offering a kind of adaptationist explanation for moralizing despite his denial that moral judgment is subserved by dedicated psychological mechanisms. Conclusion Adaptationist accounts of morality attempt to explain the evolution of morality in terms of the selective advantage that judging in moral terms secured for our distant ancestors. Prinz presents his by-product explanation of morality as an alternative to adaptationist accounts, but the two are not incompatible. The lack of psychological mechanisms dedicated to moral judgment does not imply that moralising is an evolutionary accident. Supposing so is a result of insufficient clarity with regard to several related but importantly distinction notions: innateness, adaptation, exaptation, spandrel, and by-product. Even if there is no psychological machinery dedicated to morality, moralising need be neither inevitable nor functionless. References Ayala F (2010) The difference of being human: morality. Proceedings of the National Academy of Sciences 107(2): 9015–9022. Bateson P (1991) The Development and Integration of Behavior. Cambridge: Cambridge University Press. 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